Prime mover of active head flexion; simultaneous contraction of both muscles causes neck flexion, generally against resistance was when one raises head when lying on back; (head flexion is ordinarily result of combined effects of gravity and regulated relaxation of head extensors); acting alone, each muscle rotates head toward shoulder on opposite side and tilts or laterally flexes head to its own side

Sternocleidomastoid innervation

Accessory nerve and branches of C2-C4

Thyrohyoid origin and insertion

origin: Thyroid cartilage; insertion: Hyoid bone

Pharyngeal Constrictor Muscles action

Working as a group, all constrict pharynx during swallowing, which propels a food bolus to esophagus